It works, but you're running single-channel.

Yes, the computer will boot and run normally with one stick.

You’ll be running in single-channel mode, which means the memory bandwidth is halved. For most daily tasks — web browsing, office work, even light gaming — you probably won’t notice. But for anything memory-intensive like video editing, 3D rendering, or fast-paced gaming, you’re leaving performance on the table.

Single channel is not broken, it’s just slower. The motherboard doesn’t care whether one slot is empty. It just treats the installed stick as a single channel.

If you plan to add a second stick later, buy the exact same model (same speed, timings, voltage) to avoid stability headaches. Or buy a matched kit now and save the headache.